Changeset 2725 in MondoRescue for branches/2.2.9/mindi-busybox/docs/nofork_noexec.txt

Timestamp:

Feb 25, 2011, 9:26:54 PM (13 years ago)

Author:

Bruno Cornec

Message:

• Update mindi-busybox to 1.18.3 to avoid problems with the tar command which is now failing on recent versions with busybox 1.7.3

File:

• branches/2.2.9/mindi-busybox/docs/nofork_noexec.txt (modified) (4 diffs)

branches/2.2.9/mindi-busybox/docs/nofork_noexec.txt

@@ -3 +3 @@
 Unix shells traditionally execute some commands internally in the attempt
 to dramatically speed up execution. It will be slow as hell if for every
-"echo blah" shell will fork and exec /bin/echo. For this end, shells
+"echo blah" shell will fork and exec /bin/echo. To this end, shells
 have to _reimplement_ these commands internally.
 
@@ -12 +12 @@
 
 Applet will be subject to NOFORK/NOEXEC tricks if it is marked as such
-in applets.h. CONFIG_FEATURE_PREFER_APPLETS is a config option which
+in applets.h. FEATURE_PREFER_APPLETS is a config option which
 globally enables usage of NOFORK/NOEXEC tricks.
+If it is enabled, FEATURE_SH_STANDALONE can be enabled too,
+and then shells will use NOFORK/NOEXEC tricks for ordinary commands.
+NB: shell builtins use these tricks regardless of FEATURE_SH_STANDALONE
+or FEATURE_PREFER_APPLETS.
 
-If you want to call a program and wait for it, use spawn_and_wait(argv).
-It will check whether argv[0] is an applet name and will optionally
-do NOFORK/NOEXEC thing.
+In C, if you want to call a program and wait for it, use
+spawn_and_wait(argv), BB_EXECVP(prog,argv) or BB_EXECLP(prog,argv0,...).
+They check whether program name is an applet name and optionally
+do NOFORK/NOEXEC thing depending on configuration.
 
-NOEXEC
+
+    NOEXEC
 
 NOEXEC applet should work correctly if another applet forks and then
@@ -33 +39 @@
 
 NOEXEC applets save only one half of fork+exec overhead.
-NOEXEC trick is disabled for NOMMU compile.
+NOEXEC trick is disabled for NOMMU build.
 
-NOFORK
+
+    NOFORK
 
 NOFORK applet should work correctly if another applet simply runs
@@ -56 +63 @@
   allocation. All other allocations should use malloc[_or_warn]().
   After first allocation, you cannot use any xfuncs.
+  Otherwise, failing xfunc will return to caller applet
+  without freeing malloced data!
 * All allocated data, opened files, signal handlers, termios settings,
   O_NONBLOCK flags etc should be freed/closed/restored prior to return.